My SWR Spellbinder Blue is ticking....

[andyhaines]

Hello All,

i’ve recently got hold of a lovely SWR Spellbinder Blue combo (valve preamp, 160w class d power amp) which seems to be in pretty good nick. It does however “tick”, well, more of a soft pop every few seconds when cold, with the frequency slowing down over time. Each time there’s a tick the mute LED beneath the master flashes on then off. Audible both through the speaker and through headphones, so I’m guessing more likely to be a preamp issue. 

Apart from calling the bomb squad, anyone any thoughts as to what may be happening? Getting the amp serviced would be a good start but struggling to find anywhere that deals with both valve and digital amps in the Bath area.

pic enclosed for gear porners...

cheers!

Andy

[itu]

Questions:

Is that Phantom power on?

Does the sound resemble a tube warming up? (Is there a tube?)

Try an earthed power socket.

Turn all knobs down, listen, and then up (except vol; maybe up to 11 o'clock) and check for possible issues.

[andyhaines]

Thanks for the tips - phantom power is off. Yes it has a tube preamp but as I’m very new to tube stuff I don’t know what a tube warming up sounds like. Power socket is earthed.

with everything down apart from the master, the popping sound is quiet but certainly there - almost like a high pitched heartbeat, with the mute light flashing every other ‘pip’. Slowly turning the gain up increases the sound of the pips (as well as a 50z hum I think).

Any of that help?

cheers!

Andy

 

[itu]

A tube / A valve, as it is glass and becomes hot, makes some noise while warming up. But that light blinking may lead to another place, maybe to a capacitor.

Capacitors get old. If you need to change them, the parts do not cost much (like £0.5 - 5 each) but the work costs something. It might be reasonable to show that amp to someone who has at least some experience in tube amps. My simple guess is that the actual work takes approx. three hours: opening and closing the unit is 1 hour, and 2 hours of desoldering and soldering the new parts. If the maker needs to visit or order parts, you may need to add that to work hours.

After such a work, the unit may work well for the next 10 - 30 years.

[itu]

An easy and common way of making a very good quality headphone amp, is to use the power amp and few high power resistors. So the issue may be in the power amp, too.

https://support.fender.com/hc/en-us/articles/115002392666-SWR-Amp-Schematics

The schema tells, that the power amp section is its own. Please check the FX-loop, just in case (put a bass cable in between). Other than that, the amp needs to be opened and measured to find the issue. There seems to be lots of TPs, there. Should help.

Edited June 11, 2019 by itu
linkin'

[andyhaines]

Very useful stuff, thanks, much appreciated.

i’d also found the same fender link to the spellbinder schematics so at least I’ve got something useful to give to an amp tech if I can find a good one locally!

Andy